Chromatography Forum

Hi all!!

Has anyone tried this mixture? I have a tablet with 500 mg of Acetaminophen and 200 mg of Carisoprodol.
I must use UV detection, sorry!

Any ideas, thanks all the same!!

You are going to have a very tough time as Carisoprodol has no UV, sorry. Just for reference, the USP method uses refractive index.

Hi AA

Yes but @ 210 nm I have a nice peak, the problem is that I have no separation from Acetaminophen, so I ask everyone on this forum for a system for separating them.
I´ve tried USP and many combinations of columns an mobile phases without succes.

I am quite surprised that you are having trouble sepearating these two, the detection should have been much more of an issue (I will guess that you have plenty of compound to look at). Any decent 150 mm C18 column should do the trick using a gradient of ACN/formic. I will give it a try this morning and let you know.

I did try this. I used an ELSD as the detector.

3.0X1500 Atlantis C18 @ 0.60 mL/min
Gradient of 95:5 to 50:50 over 15 minutes
A=0.1% Formic in water
B=0.1% Formic in CH3CN

Acetaminophen @ ~ 2.5 minutes
Carisoprodol @ ~ 15 minutes

I think the problem is the UV detection. For your purposes, I would use the method suggested by AA without the formic acid in the mobile phase. Just water/acetonitrile will do fine.

By the way, this is not a developed method, this just shows that these compound are easily separated.

Hi, AA & Uwe

Thanks both for the input, I will try your suggestions. I have no other detector available than UV, by the way I´m sorry for my ignorance but what is the meaning of ELSD?

Many thanks to you!!

ELSD=Evaporative Light Scattering Detector